Phthalazinone derivatives

ABSTRACT

4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one as crystalline Form A.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/829,694, filed Oct. 17, 2006, which is incorporated herein byreference in its entirety.

The present invention relates to a crystalline form and improved methodsof synthesis of a particular phthalazinone derivative, intermediates inthe synthesis and pharmaceutical compositions and uses of thecrystalline form.

The mammalian enzyme PARP (a 113-kDa multidomain protein) has beenimplicated in the signalling of DNA damage through its ability torecognize and rapidly bind to DNA single or double strand breaks(D'Amours, et al., Biochem. J., 342, 249-268 (1999)).

Several observations have led to the conclusion that PARP participatesin a variety of DNA-related functions including gene amplification, celldivision, differentiation, apoptosis, DNA base excision repair and alsoeffects on telomere length and chromosome stability (d' Adda di Fagagna,et al., Nature Gen., 23(1), 76-80 (1999)).

Studies on the mechanism by which PARP modulates DNA repair and otherprocesses has identified its importance in the formation ofpoly(ADP-ribose) chains within the cellular nucleus (Althaus, F. R. andRichter, C., ADP-Ribosylation of Proteins: Enzymology and BiologicalSignificance, Springer-Verlag, Berlin (1987)). The DNA-bound, activatedPARP utilizes NAD to synthesize poly(ADP-ribose) on a variety of nucleartarget proteins, including topoisomerase, histones and PARP itself(Rhun, et al., Biochem. Biophys. Res. Commun., 245, 1-10 (1998))

Poly(ADP-ribosyl)ation has also been associated with malignanttransformation. For example, PARP activity is higher in the isolatednuclei of SV40-transformed fibroblasts, while both leukemic cells andcolon cancer cells show higher enzyme activity than the equivalentnormal leukocytes and colon mucosa (Miwa, et al., Arch. Biochem.Biophys., 181, 313-321 (1977); Burzio, et al., Proc. Soc. Exp. Biol.Med., 149, 933-938 (1975); and Hirai, et al., Cancer Res., 43, 3441-3446(1983)).

A number of low-molecular-weight inhibitors of PARP have been used toelucidate the functional role of poly(ADP-ribosyl)ation in DNA repair.In cells treated with alkylating agents, the inhibition of PARP leads toa marked increase in DNA-strand breakage and cell killing (Durkacz, etal., Nature, 283, 593-596 (1980); Berger, N. A., Radiation Research,101, 4-14 (1985)).

Subsequently, such inhibitors have been shown to enhance the effects ofradiation response by suppressing the repair of potentially lethaldamage (Ben-Hur, et al., British Journal of Cancer, 49 (Suppl. VI),34-42 (1984); Schlicker, et al., Int. J. Radiat Bioi., 75, 91-100(1999)). PARP inhibitors have been reported to be effective in radiosensitising hypoxic tumour cells (U.S. Pat. No. 5,032,617; U.S. Pat. No.5,215,738 and U.S. Pat. No. 5,041,653).

Furthermore, PARP knockout (PARP −/−) animals exhibit genomicinstability in response to alkylating agents and γ-irradiation (Wang, etal., Genes Dev., 9, 509-520 (1995); Menissier de Murcia, et al., Proc.Natl. Acad. Sci. USA, 94, 7303-7307 (1997)).

A role for PARP has also been demonstrated in certain vascular diseases,septic shock, ischaemic injury and neurotoxicity (Cantoni, et al.,Biochim. Biophys. Acta, 1014, 1-7 (1989); Szabo, et al., J. Clin.Invest, 100, 723-735 (1997)). Oxygen radical DNA damage that leads tostrand breaks in DNA, which are subsequently recognised by PARP, is amajor contributing factor to such disease states as shown by PARPinhibitor studies (Cosi, et al., J. Neurosci. Res., 39, 38-46 (1994);Said, et al., Proc. Natl. Acad. Sci. U.S.A., 93, 4688-4692 (1996)). Morerecently, PARP has been demonstrated to play a role in the pathogenesisof haemorrhagic shock (Liaudet, et al., Proc. Natl. Acad. Sci. U.S.A.,97(3), 10203-10208 (2000)).

It has also been demonstrated that efficient retroviral infection ofmammalian cells is blocked by the inhibition of PARP activity. Suchinhibition of recombinant retroviral vector infections was shown tooccur in various different cell types (Gaken, et al., J. Virology,70(6), 3992-4000 (1996)). Inhibitors of PARP have thus been developedfor the use in anti-viral therapies and in cancer treatment (WO91/18591).

Moreover, PARP inhibition has been speculated to delay the onset ofaging characteristics in human fibroblasts (Rattan and Clark, Biochem.Biophys. Res. Comm., 201(2), 665-672 (1994)). This may be related to therole that PARP plays in controlling telomere function (d'Adda diFagagna, et al., Nature Gen., 23(1), 76-80 (1999)).

WO 2004/080976 discloses a number of phthalazinone derivatives, theiractivity in inhibiting PARP, and their consequential use in treatingcancer, whether as an adjunct to radiotherapy or chemotherapy, or as astand alone agent.

WO 2005/053662 describes the use of PARP inhibitors, in particularphthalazinone derivatives, as base excision repair (BER) inhibitors. Theuse of these inhibitors in the manufacture of medicaments for thetreatment of cancers which are deficient in Homologous Recombination(HR) dependent DNA DSB repair activity, in particular for cancers whichhave a BRCA1 and/or a BRCA2 deficient phenotype, is described.

4-[3-(4-Cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) disclosed in WO 2004/080976:

is of particular interest.

In WO 2004/080976, compound A was synthesised as one of a number oflibrary compounds from4-[4-fluoro-3-(piperazine-1-carbonyl)-benzyl]-2H-phthalazin-1-one(compound B):

by the addition of cyclopropanecarbonyl chloride:

to a solution of (B) in dichloromethane, followed by Hünig's base(N,N-diisopropylethyl amine). This reaction is carried out with stirringat room temperature for 16 hours, and the resulting compound beingpurified by preparative HPLC.

The piperazine derivative (B) was prepared by deprotecting4-[2-fluoro-5-(4-oxo-3,4-dihydro-phthalazin-1-ylmethyl)-benzoyl]-piperazine-1-carboxylicacid tert-butyl ester (compound C):

by the use of 6M HCl and ethanol for 1 hour, followed by basificationwith ammonia to pH 9, and extraction into dichloromethane.

The Boc-protected piperazine derivative (C) was prepared from2-fluoro-5-(4-oxo-3,4-dihydro-phthalazin-1-ylmethyl)-benzoic acid(compound D):

by the addition of piperazine-1-carboxylic acid tert-butyl ester:

2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate(HBTU) and N,N,-diisopropylethylamine in dimethylacetamide, followed bystirring for 18 hours.

Particular forms of compound A may have advantageous properties, forexample with regard to their solubility and/or their stability and/ortheir bioavailability and/or their impurity profile and/or theirfiltration characteristics and/or their drying characteristics and/ortheir lack of hygroscopicity, and/or they may be easier to handle and/ormicronise and/or form into tablets. It is also desired to have animproved method of synthesis that is suitable for synthesis of compoundA on a multi-gram scale.

Accordingly, a first aspect of the present invention provides4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) substantially in crystalline form, and in particular inForm A.

“Substantially in crystalline form” as used above, means that at least50% by weight of compound A is in crystalline form, preferably at least70% by weight, 80% or 90% by weight. In some embodiments, at least 95%by weight, 99% by weight or even 99.5% or more by weight may be incrystalline form.

Compound A as crystalline Form A has an X-ray diffraction pattern(λ=1.5418 Å) containing specific peaks at:

Peak 2θ° (±0.1°) 1 12.0 2 17.8 3 21.1 4 22.3 5 29.2

Compound A as crystalline form A may also have the following additionalpeaks an X-ray diffraction pattern (λ=1.5418 Å):

Peak 2θ° (±0.1°) 6 10.5 7 14.0 8 21.7 9 24.3 10 26.1

Compound A as crystalline Form A may also be characterised by anycombination of three or more peaks selected from the list of 10 peaksabove.

A representative powder XRD pattern of compound A as Form A is shown inFIG. 3.

Without wishing to be bound by theory, compound A is able to readilyform a structure in which solvent molecules can occupy positions withinthe crystal lattice. Such solvates, not necessarily stoichiometric innature, can consist of one pure solvate (e.g. Compound A methanolate,and Compound A Tetrahydrofuranate) or potentially can consist of morethan one solvent component (e.g. methanol and di-ethyl ether). Thesolvent molecules typically lie within pockets created by the Compound Amolecules. In certain circumstances, the volume of these pockets aresufficiently flexible to incorporate a range of solvents, resulting inlittle change in the overall structure of the material, and hence onlysmall shifts in the XRPD reflections.

Solvates, including those which share the same overall structure, arisefrom solution maturation and crystallisation experiments fromdichloromethane, ethyl acetate, methanol, ethanol, isopropanol,2-butanone, t-butyl methyl ether, toluene, tetrahydrofuran, water,cyclohexane, cyclopropyl methyl ketone, 1,2 dichloroethane, ethyltrifluoroacetate, fluorobenzenehexafluoro-iso-propanol, methylnonafluorobutyl ether, 2-methyl-1-propanol, nitromethane, propionitrile,trichloroethylene, ααα-trifluorotoluene, heptane, dioxane, acetonitrile,either as pure solvents or when combined with another solvent. The X-raydiffraction pattern of the most common solvate structure is shown inFIG. 4, and typically contains most intense peaks at positions listedbelow:

2θ° (±0.1°) Peak (λ = 1.5418 Å) 1 7.0-7.5 2 10.1-10.6 3 15.1-15.6 418.5-19.0 5 21.0-21.5 6 24.8-25.3 7 27.0-27.5

It will be understood that the relative intensities of peaks shown inthe figures may vary according to the orientation of the sample undertest and on the type and setting of the instrument used so that theintensities in the XRD traces included herein are illustrative and notintended to be used for absolute comparison.

Form A of compound A is substantially free from solvent. The term“substantially free from solvent” as used herein refers to the formhaving only insignificant amounts of any solvent, e.g. a form with atotal of 0.5% by weight or less of any solvent. The total amount of anysolvent, including water, may be 0.25%, 0.1%, 0.05% or 0.025% by weightor less.

Form A of compound A may also be characterised using DSC. Form A ofcompound A when heated from 25° C. to 325° C. at 10° C. per minute willbegin melting at 210.1° C.±1° C. A representative DSC trace for compoundA as Form A is shown in FIG. 5.

The second aspect of the present invention provides a method ofobtaining4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) as crystalline Form A which comprises crystallisingcompound A in a solvent and then displacing the solvent from thecrystalline form with a displacing agent. The displacing agent may bewater or a mixture of a C₁₋₂ alcohol and water.

In a first embodiment, this method comprises the steps of:

(i) crystallising4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) from a solvent;

(ii) if the original solvent is not ethanol, treating the crystallinecompound A with ethanol;

(iii) treating the crystalline compound A with water to remove trappedethanol;

(iv) drying the resulting product.

The solvent used in the original crystallisation may be, for example,dichloromethane or acetonitrile.

The methods for obtaining Form A may generally involve solventreplacement. It has been found that compound A crystallises in such away that channels in the crystal lattice are formed which can trapsolvents, thus making them difficult to remove.

The method of the first embodiment can be used in particular if thesolvent used in the crystallisation of compound A is dichloromethane.The step of exchanging the dichloromethane as a solvent with ethanol asa solvent can be carried out by distilling the solution of compound A atatmospheric pressure in the presence of ethanol. The exchange iscomplete when the head temperature approaches the boiling point ofethanol, e.g. at least 73° C. In particular, the exchange may be carriedout by distilling out the majority of the DCM, then adding a volume ofethanol. The distillation is then continued, with replacing batches ofdistillate with equal volumes of ethanol.

Crystallising compound A from the ethanol solvent may be carried out bycooling the solution to below 15° C., preferably less than 10° C., andmore preferably to about 8° C. The crystals of compound A may then beremoved from solution by filtration.

The crystalline compound A may be treated with water to remove trappedethanol by suspended the crystalline material in water and heating atreflux for a sufficient time, for example at least three hours, andpreferably for about four hours. The crystalline compound A may beremoved from suspension in water by filtration.

Drying the resulting product of the above step is readily achieved. Forexample, by heating the product in an oven at a temperature of at least60° C., preferably at about 70° C.

In another such embodiment, the method comprises the steps of:

(i) obtaining compound A as crystalline form containing solvent;

(ii) if the original solvent used in the synthesis of compound A in thecrystalline form is not a mixture of water and a C₁₋₂ alcohol (i.e.methanol, ethanol), treating compound A in the crystalline form with amixture of water and a C₁₋₂ alcohol;

(ii) drying the resulting product.

The resulting product can be further treated with a mixture of water anda C₁₋₂ alcohol, and dried in order to further isolate compound A in acrystalline Form A.

The mixture of water and C₁₋₂ alcohol is preferably in the range of 2:1to 1:2 by volume, and more preferably 1.5:1 to 1:1.5 by volume. Aparticularly preferred mixture is 1 part water to 1.2 parts C₁₋₂alcohol. Another particularly preferred mixture is 2 parts water to 1part C₁₋₂ alcohol. The C₁₋₂ alcohol is preferably ethanol.

Compound A as crystalline Form may be obtained by crystallisation of thecompound A from a solvent, as described above.

The solvent treatment in step (ii) may be carried out by suspendingcompound A in the mixture of water and C₁₋₂ alcohol and heating toreflux with stirring. This may be followed by cooling to between 55 and65° C. and filtering, e.g. through a celite pad. The filter pad may bewashed with a mixture of water and C₁₋₂ alcohol before being distilledat ambient pressure (usually 1 atm), or above. The distillation may bestopped to yield a suspension that is left at room temperature beforesubsequent filtration. The resulting filter cake may be washed withwater.

Drying the resulting product of the above step is readily achieved. Forexample, by heating the product in an oven at a temperature of at least50° C., preferably at about 60° C.

The further treatment may proceed in a similar manner to that describedabove.

In a third embodiment, the method comprises:

(i) suspending compound A in a mixture of water and a C₁₋₂ alcohol asthe solvent;

(ii) heating the suspension to reflux;

(iii) cooling the solution and seeding with compound A as Form A;

(iv) drying the resulting product.

The resulting product can be further treated with a mixture of water anda C₁₋₂ alcohol, and dried in order to further isolate compound A in acrystalline Form A.

The mixture of water and C₁₋₂ alcohol is preferably in the range of 2:1to 1:5 by volume, and more preferably 1:2 to 1:4 by volume. Aparticularly preferred mixture is 1 part water to 3 parts C₁₋₂ alcohol.The C₁₋₂ alcohol is preferably ethanol.

Step (iii) may comprise cooling the solution to between 65 and 75° C.(e.g. 70° C.) and filtering, e.g. through a celite pad. The filter padmay be washed with a mixture of water and C₁₋₂ alcohol before beingdistilled (e.g. at ambient pressure, or above). The seeding may occurafter the resulting filtrate has been cooled to between 40 and 50° C.(e.g. 45° C.). The resulting suspension may be cooled to ambienttemperature (e.g. 20° C.) in between 2 and 3 hours (e.g. 2.5 hours) andmaintained at said temperature for long enough to establishcrystallisation. This may be between 12 and 24 hours, and may be forabout 16 hours. At the end of this period, further water may be added.The amount may be about equal to the volume of total solvent (water andC₁₋₂ alcohol) present and may be added slowly, for example over a periodof 4 to 6 (e.g. 5) hours. The suspension may be held at ambienttemperature after the water addition, for example for 2 hours.

The suspension may then be filtered, and the resulting filter cake maybe washed with a mixture of C₁₋₂ alcohol and water (in a ratio ofbetween 1:3 and 1:2, e.g. 1:2.3).

Drying the resulting product of the above step is readily achieved. Forexample, by heating the product in an oven under vacuum at a temperatureof between 40 and 60° C.

A third aspect of the present invention provides a method ofsynthesising compound A from compound B comprising the step of:

-   -   (i) adding a pre-mixed solution of triethylamine and        cyclopropane carbonyl chloride, in an appropriate organic        solvent (for example, DCM (dichloromethane)) in a controlled        manner, to compound B in the same organic solvent with the        temperature of the solution being controlled to be below 20° C.

In some embodiments, the method further comprises the step of:

-   -   (ii) agitating (e.g. stirring) the resulting solution from (i)        until the reaction is complete, whilst maintaining the        temperature of the solution below 20° C.

The addition in step (i) may take place in a dropwise manner

This method is more controlled than that described in WO 2004/080976,resulting in a more regioselective addition of the acid chloride. Theless controlled method of the prior art can lead to addition of the acidchloride at the phthalazinone nitrogen and or oxygen, as well as at thedesired piperidine nitrogen.

It is preferred that the above method is carried out under a nitrogenatmosphere.

It is further preferred that the temperature of the solution in stage(ii) is maintained between 10 and 15° C.

The product of the above reaction is preferably worked up by at leastone water washing step. More preferably the work up contains an initialand final water washing steps, and intermediate washing steps using adilute acid, e.g. 5% citric acid solution, followed by a dilute base,e.g. 5% sodium carbonate solution.

A fourth aspect of the present invention provides a method ofsynthesising compound A from compound D comprising reacting compound Dwith 1-(cyclopropylcarbonyl)piperazine, or a mineral acid salt thereof,in the presence of an amide coupling agent and a base, for example, anamine (e.g. a tertiary amine, such as diisopropylethylamine).

The mineral acid salt may be, for example, the hydrochloride salt.

The addition of 1-(cyclopropylcarbonyl)piperazine, or a mineral acidsalt thereof, to compound D may be carried out in any suitable solvent,for example, acetonitrile. The amide coupling agent is preferably2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate(HBTU). It is preferably added to the solution of1-(cyclopropylcarbonyl)piperazine, or its mineral acid salt,diisopropylethylamine and compound D over a period of time, for example30 minutes. The temperature of the resulting solution may be maintainedat 25° C. or below (or 20° C. or below, e.g. at 18° C.). After itsaddition, the resulting solution may be left to stand for a period oftime. A preferred temperature regime is holding the solution at roomtemperature for 2 hours.

The resulting compound A may be removed from the solution by cooling tobelow 10° C. (or below 5° C., for example, 3° C.) for a period of time(e.g. 1 hour), followed by filtration. The resulting compound A may bewashed, for example, with cold acetonitrile.

In WO 2004/080976, the following route to compound D is disclosed:

Dimethyl phosphite was added drop-wise to a solution of sodium methoxidein methanol at 0° C. 2-Carboxybenzaldehyde (H) was then addedportion-wise to the reaction mixture as a slurry in methanol, with thetemperature kept below 5° C. The resulting pale yellow solution waswarmed to 20° C. over 1 hour. Methanesulphonic acid was added to thereaction drop-wise and the resulting white suspension was evaporated invacuo. The white residue was quenched with water and extracted intochloroform. The combined organic extracts were washed with water, driedover MgSO₄, and evaporated in vacuo to yield(3-oxo-1,3-dihydro-isobenzofuran-1-yl)phosphonic acid dimethyl ester (G)as a white solid (yield: 95%). This was then used without furtherpurification in the next stage.

To a mixture of (3-oxo-1,3-dihydro-isobenzofuran-1-yl)phosphonic aciddimethyl ester (G) in tetrahydrofuran and 2-fluoro-5-formylbenzonitrile(F) in tetrahydrofuran was added triethylamine drop-wise over 25 min,with the temperature kept below 15° C. The reaction mixture was warmedslowly to 20° C. over 1 hour and concentrated in vacuo. The whiteresidue was slurried in water or 30 minutes, filtered, washed withwater, hexane and ether, and dried to yield2-fluoro-5-(3-oxo-3H-isobenzofuran-1-ylidenemethyl)benzonitrile (E) as a50:50 mixture of E and Z isomers (yield: 96%).

To a suspension of2-fluoro-5-(3-oxo-3H-isobenzofuran-1-ylidenemethyl)benzonitrile (E) inwater was added aqueous sodium hydroxide solution and the reactionmixture was heated under nitrogen to 90° C. for 30 minutes. The reactionmixture was partially cooled to 70° C., and hydrazine hydrate was addedand stirred for 18 hours at 70° C. The reaction was cooled to roomtemperature and acidified with 2M HCl to pH 4. The mixture was stirredfor 10 minutes and filtered. The resulting solid was washed with water,hexane, ether, ethyl acetate and dried to yield compound D as a palepink powder (yield: 77%).

It is also desired to have an improved method of synthesis of compoundD.

Accordingly a fifth aspect of the present invention provides a methodsynthesising compound D, comprising the step of:

(a) synthesising diethyl(3-oxo-1,3-dihydro-2-benzofuran-1-yl)phosphonate (G′) from2-carboxybenzaldehyde (H);

(b) synthesising2-fluoro-5-[(E/Z)-(3-oxo-2-benzofuran-1(3H)-ylidene)methyl]benzonitrile(E) from diethyl (3-oxo-1,3-dihydro-2-benzofuran-1-yl)phosphonate.

It is preferred that compound G′ is not isolated in the synthesis. Thismethod avoids the use of the sodium salt of dimethylphosphite which isunstable (Pelchowicz, et al., J. Chem. Soc, 4348-4350 (1961)) inalcoholic solution. It is preferred that the step (a) occurs in2-methyltetrahydrofuran in which the sodium salt of diethyl phosphite isstable. This salt may be formed in situ by adding diethyl phosphite to acooled solution of sodium t-amylate in 2-methyltetrahydrofuran. Thereaction with the sodium salt of diethyl phosphite may be followed byreaction with methanesulphonic acid.

Step (b) may be carried out in 2-methyltetrahydrofuran, with theaddition of triethylamine.

The method of synthesising compound D may further comprise the step of:

(c) synthesising2-fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzonitrile (ED):

from compound E by reaction with hydrazine hydrate; and(d) synthesising compound D from compound ED by reaction with sodiumhydroxide.

Step (c) may be achieved by using between 1.1 and 1.3 equivalents ofhydrazine hydrate in tetrahydrofuran followed by neutralisation of theexcess hydrazine hydrate using acetic acid.

A sixth aspect of the present invention provides the compound ED:

and its use in the synthesis of compound D.

A further aspect of the invention provides a mineral acid salt of1-(cyclopropylcarbonyl)piperazine, and a method of synthesis thereof byreacting piperazine with acetic acid, followed by addition ofcyclopropanecarbonyl chloride.

A seventh aspect of the present invention provides a pharmaceuticalcomposition comprising a compound of the first aspect and apharmaceutically acceptable carrier or diluent.

An eighth aspect of the present invention provides a compound of thefirst aspect for use in a method of treatment of the human or animalbody.

A ninth aspect of the present invention provides the use of a compoundas defined in the first aspect of the invention in the preparation of amedicament for inhibiting the activity of PARP.

Further aspects of the invention provide the use of a compound asdefined in the first aspect of the invention in the preparation of amedicament for the treatment of: vascular disease; septic shock;ischaemic injury; neurotoxicity; haemorraghic shock; viral infection; ordiseases ameliorated by the inhibition of the activity of PARP.

Another further aspect of the invention provides for the use of acompound as defined in the first aspect of the invention in thepreparation of a medicament for use as an adjunct in cancer therapy orfor potentiating tumour cells for treatment with ionizing radiation orchemotherapeutic agents.

Other further aspects of the invention provide for the treatment ofdisease ameliorated by the inhibition of PARP, comprising administeringto a subject in need of treatment a therapeutically-effective amount ofa compound as defined in the first aspect, preferably in the form of apharmaceutical composition and the treatment of cancer, comprisingadministering to a subject in need of treatment atherapeutically-effective amount of a compound as defined in the firstaspect in combination, preferably in the form of a pharmaceuticalcomposition, simultaneously or sequentially with ionizing radiation orchemotherapeutic agents.

In further aspects of the present invention, the compounds may be usedin the preparation of a medicament for the treatment of cancer which isdeficient in Homologous Recombination (HR) dependent DNA DSB repairactivity, or in the treatment of a patient of a cancer which isdeficient in HR dependent DNA DSB repair activity, comprisingadministering to said patient a therapeutically-effective amount of thecompound.

The HR dependent DNA DSB repair pathway repairs double-strand breaks(DSBs) in DNA via homologous mechanisms to reform a continuous DNA helix(K. K. Khanna and S. P. Jackson, Nat. Genet. 27(3): 247-254 (2001)). Thecomponents of the HR dependent DNA DSB repair pathway include, but arenot limited to, ATM (NM_(—)000051), RAD51 (NM_(—)002875), RAD51L1(NM_(—)002877), RAD51C (NM_(—)002876), RAD51L3 (NM_(—)002878), DMC1(NM_(—)007068), XRCC2 (NM_(—)005431), XRCC3 (NM_(—)005432), RAD52(NM_(—)002879), RAD54L (NM_(—)003579), RAD54B (NM_(—)012415), BRCA1(NM_(—)007295), BRCA2 (NM_(—)000059), RAD50 (NM_(—)005732), MRE11A(NM_(—)005590) and NBS1 (NM_(—)002485). Other proteins involved in theHR dependent DNA DSB repair pathway include regulatory factors such asEMSY (Hughes-Davies, et al., Cell, 115, pp 523-535). HR components arealso described in Wood, et al., Science, 291, 1284-1289 (2001).

A cancer which is deficient in HR dependent DNA DSB repair may compriseor consist of one or more cancer cells which have a reduced or abrogatedability to repair DNA DSBs through that pathway, relative to normalcells i.e. the activity of the HR dependent DNA DSB repair pathway maybe reduced or abolished in the one or more cancer cells.

The activity of one or more components of the HR dependent DNA DSBrepair pathway may be abolished in the one or more cancer cells of anindividual having a cancer which is deficient in HR dependent DNA DSBrepair. Components of the HR dependent DNA DSB repair pathway are wellcharacterised in the art (see for example, Wood, et al., Science, 291,1284-1289 (2001)) and include the components listed above.

In some preferred embodiments, the cancer cells may have a BRCA1 and/ora BRCA2 deficient phenotype i.e. BRCA1 and/or BRCA2 activity is reducedor abolished in the cancer cells. Cancer cells with this phenotype maybe deficient in BRCA1 and/or BRCA2, i.e. expression and/or activity ofBRCA1 and/or BRCA2 may be reduced or abolished in the cancer cells, forexample by means of mutation or polymorphism in the encoding nucleicacid, or by means of amplification, mutation or polymorphism in a geneencoding a regulatory factor, for example the EMSY gene which encodes aBRCA2 regulatory factor (Hughes-Davies, et al., Cell, 115, 523-535).

BRCA1 and BRCA2 are known tumour suppressors whose wild-type alleles arefrequently lost in tumours of heterozygous carriers (Jasin M., Oncogene,21(58), 8981-93 (2002); Tutt, et al., Trends Mol. Med., 8(12), 571-6,(2002)). The association of BRCA1 and/or BRCA2 mutations with breastcancer is well-characterised in the art (Radice, P. J., Exp Clin CancerRes., 21(3 Suppl), 9-12 (2002)). Amplification of the EMSY gene, whichencodes a BRCA2 binding factor, is also known to be associated withbreast and ovarian cancer.

Carriers of mutations in BRCA1 and/or BRCA2 are also at elevated risk ofcancer of the ovary, prostate and pancreas.

In some preferred embodiments, the individual is heterozygous for one ormore variations, such as mutations and polymorphisms, in BRCA1 and/orBRCA2 or a regulator thereof. The detection of variation in BRCA1 andBRCA2 is well-known in the art and is described, for example in EP 699754, EP 705 903, Neuhausen, S. L. and Ostrander, E. A., Genet. Test, 1,75-83 (1992); Chappnis, P. O. and Foulkes, W. D., Cancer Treat Res, 107,29-59 (2002); Janatova M., et al., Neoplasma, 50(4), 246-50 (2003);Jancarkova, N., Ceska Gynekol., 68(1), 11-6 (2003)). Determination ofamplification of the BRCA2 binding factor EMSY is described inHughes-Davies, et al., Cell, 115, 523-535).

Mutations and polymorphisms associated with cancer may be detected atthe nucleic acid level by detecting the presence of a variant nucleicacid sequence or at the protein level by detecting the presence of avariant (i.e. a mutant or allelic variant) polypeptide.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows the NMR of compound A after water treatment (example 1);

FIG. 2 shows the powder XRD pattern of compound A as Form A after watertreatment (example 1);

FIG. 3 shows a representative powder XRD pattern of compound A as FormA;

FIG. 4 shows a representative powder XRD pattern of compound A assolvated form;

FIG. 5 shows a representative DSC trace of compound A as Form A obtainedby heating from 25° C. to 325° C. at 10° C. per minute.

USE

The present invention provides compound A as Form A as an activecompound, specifically, active in inhibiting the activity of PARP.

The term “active” as used herein, pertains to the compound which iscapable of inhibiting PARP activity. One assay which may conveniently beused in order to assess the PARP inhibition offered by the compound isdescribed in the examples below.

The present invention further provides a method of inhibiting theactivity of PARP in a cell, comprising contacting said cell with aneffective amount of the active compound, preferably in the form of apharmaceutically acceptable composition. Such a method may be practisedin vitro or in vivo.

For example, a sample of cells may be grown in vitro and the activecompound brought into contact with said cells, and the effect of thecompound on those cells observed. As examples of “effect”, the amount ofDNA repair effected in a certain time may be determined. Where theactive compound is found to exert an influence on the cells, this may beused as a prognostic or diagnostic marker of the efficacy of thecompound in methods of treating a patient carrying cells of the samecellular type.

The term “treatment”, as used herein in the context of treating acondition, pertains generally to treatment and therapy, whether of ahuman or an animal (e.g. in veterinary applications), in which somedesired therapeutic effect is achieved, for example, the inhibition ofthe progress of the condition, and includes a reduction in the rate ofprogress, a halt in the rate of progress, amelioration of the condition,and cure of the condition. Treatment as a prophylactic measure (i.e.prophylaxis) is also included.

The term “adjunct” as used herein relates to the use of the activecompound in conjunction with known therapeutic means. Such means includecytotoxic regimes of drugs and/or ionising radiation as used in thetreatment of different cancer types. In particular, the active compoundsare known to potentiate the actions of a number of cancer chemotherapytreatments, which include the topoisomerase class of poisons (e.g.topotecan, irinotecan, rubitecan), most of the known alkylating agents(e.g. DTIC, temozolamide) and platinum based drugs (e.g. carboplatin,cisplatin) used in treating cancer.

The active compound may also be used as cell culture additives toinhibit PARP, for example, in order to sensitize cells to knownchemotherapeutic agents or ionising radiation treatments in vitro.

The active compound may also be used as part of an in vitro assay, forexample, in order to determine whether a candidate host is likely tobenefit from treatment with the compound in question.

Administration

The active compound or pharmaceutical composition comprising the activecompound may be administered to a subject by any convenient route ofadministration, whether systemically/peripherally or at the site ofdesired action, including but not limited to, oral (e.g. by ingestion);topical (including e.g. transdermal, intranasal, ocular, buccal, andsublingual); pulmonary (e.g. by inhalation or insufflation therapyusing, e.g. an aerosol, e.g. through mouth or nose); rectal; vaginal;parenteral, for example, by injection, including subcutaneous,intradermal, intramuscular, intravenous, intraarterial, intracardiac,intrathecal, intraspinal, intracapsular, subcapsular, intraorbital,intraperitoneal, intratracheal, subcuticular, intraarticular,subarachnoid, and intrasternal; by implant of a depot, for example,subcutaneously or intramuscularly.

The subject may be a eukaryote, an animal, a vertebrate animal, amammal, a rodent (e.g. a guinea pig, a hamster, a rat, a mouse), murine(e.g. a mouse), canine (e.g. a dog), feline (e.g. a cat), equine (e.g. ahorse), a primate, simian (e.g. a monkey or ape), a monkey (e.g.marmoset, baboon), an ape (e.g. gorilla, chimpanzee, orangutan, gibbon),or a human.

Formulations

While it is possible for the active compound to be administered alone,it is preferable to present it as a pharmaceutical composition (e.g.,formulation) comprising the active compound, as defined above, togetherwith one or more pharmaceutically acceptable carriers, adjuvants,excipients, diluents, fillers, buffers, stabilisers, preservatives,lubricants, or other materials well known to those skilled in the artand optionally other therapeutic or prophylactic agents.

Thus, the present invention further provides pharmaceuticalcompositions, as defined above, and methods of making a pharmaceuticalcomposition comprising admixing the active compound, as defined above,together with one or more pharmaceutically acceptable carriers,excipients, buffers, adjuvants, stabilisers, or other materials, asdescribed herein, such that active compound remains as crystalline FormA.

The term “pharmaceutically acceptable” as used herein pertains tocompounds, materials, compositions, and/or dosage forms which are,within the scope of sound medical judgement, suitable for use in contactwith the tissues of a subject (e.g. human) without excessive toxicity,irritation, allergic response, or other problem or complication,commensurate with a reasonable benefit/risk ratio. Each carrier,excipient, etc. must also be “acceptable” in the sense of beingcompatible with the other ingredients of the formulation.

Suitable carriers, diluents, excipients, etc. can be found in standardpharmaceutical texts. See, for example, “Handbook of PharmaceuticalAdditives”, 2nd Edition (eds. M. Ash and 1. Ash), 2001 (SynapseInformation Resources, Inc., Endicott, N.Y., USA), “Remington'sPharmaceutical Sciences”, 20th edition, pub. Lippincott, Williams &Wilkins, 2000; and “Handbook of Pharmaceutical Excipients”, 2nd edition,1994.

The formulations may conveniently be presented in unit dosage form andmay be prepared by any methods well known in the art of pharmacy. Suchmethods include the step of bringing into association the activecompound with the carrier which constitutes one or more accessoryingredients. In general, the formulations are prepared by uniformly andintimately bringing into association the active compound with liquidcarriers or finely divided solid carriers or both, and then if necessaryshaping the product.

Formulations may be in the form of suspensions, tablets, granules,powders, capsules, cachets, pills or pastes.

Formulations suitable for oral administration (e.g., by ingestion) maybe presented as discrete units such as capsules, cachets or tablets,each containing a predetermined amount of the active compound; as apowder or granules; as a suspension in an aqueous or non-aqueous liquid;or as a paste.

A tablet may be made by conventional means, e.g. compression or molding,optionally with one or more accessory ingredients. Compressed tabletsmay be prepared by compressing in a suitable machine the active compoundin a free-flowing form such as a powder or granules, optionally mixedwith one or more binders (e.g. povidone, gelatin, acacia, sorbitol,tragacanth, hydroxypropylmethyl cellulose); fillers or diluents (e.g.lactose, microcrystalline cellulose, calcium hydrogen phosphate);lubricants (e.g. magnesium stearate, talc, silica); disintegrants (e.g.sodium starch glycolate, cross-linked povidone, cross-linked sodiumcarboxymethyl cellulose); surface-active or dispersing or wetting agents(e.g., sodium lauryl sulfate); and preservatives (e.g., methylp-hydroxybenzoate, propyl p-hydroxybenzoate, sorbic acid). Moldedtablets may be made by molding in a suitable machine a mixture of thepowdered compound moistened with an inert liquid diluent. The tabletsmay optionally be coated or scored and may be formulated so as toprovide slow or controlled release of the active compound therein using,for example, hydroxypropylmethyl cellulose in varying proportions toprovide the desired release profile. Tablets may optionally be providedwith an enteric coating, to provide release in parts of the gut otherthan the stomach.

A capsule may include the active compound in suspension.

Formulations suitable for topical administration (e.g. transdermal,intranasal, ocular, buccal, and sublingual) may be formulated as apaste.

Formulations suitable for topical administration to the eye also includeeye drops wherein the active compound is suspended in a suitablecarrier, especially an aqueous solvent for the active compound.

Formulations suitable for nasal administration, wherein the carrier is asolid, include a coarse powder having a particle size, for example, inthe range of about 20 to about 500 microns which is administered in themanner in which snuff is taken, i.e. by rapid inhalation through thenasal passage from a container of the powder held close up to the nose.

Formulations suitable for administration by inhalation include thosepresented as an aerosol spray from a pressurised pack, with the use of asuitable propellant, such as dichlorodifluoromethane,trichlorofluoromethane, dichloro-tetrafluoroethane, carbon dioxide, orother suitable gases.

Dosage

It will be appreciated that appropriate dosages of the active compound,and compositions comprising the active compound, can vary from patientto patient. Determining the optimal dosage will generally involve thebalancing of the level of therapeutic benefit against any risk ordeleterious side effects of the treatments of the present invention. Theselected dosage level will depend on a variety of factors including, butnot limited to, the activity of the particular compound, the route ofadministration, the time of administration, the rate of excretion of thecompound, the duration of the treatment, other drugs, compounds, and/ormaterials used in combination, and the age, sex, weight, condition,general health, and prior medical history of the patient. The amount ofcompound and route of administration will ultimately be at thediscretion of the physician, although generally the dosage will be toachieve local concentrations at the site of action which achieve thedesired effect without causing substantial harmful or deleteriousside-effects.

Administration in vivo can be effected in one dose, continuously orintermittently (e.g., in divided doses at appropriate intervals)throughout the course of treatment. Methods of determining the mosteffective means and dosage of administration are well known to those ofskill in the art and will vary with the formulation used for therapy,the purpose of the therapy, the target cell being treated, and thesubject being treated. Single or multiple administrations can be carriedout with the dose level and pattern being selected by the treatingphysician.

In general, a suitable dose of the active compound is in the range ofabout 10 mg to about 600 mg per m² body area weight of the subject perday.

EXAMPLES Example 1 Synthesis of Compound A

Starting material (D) was synthesised by the method disclosed in WO2004/080976

Methods

Preparative HPLC

Samples were purified with a Waters mass-directed purification systemutilising a Waters 600 LC pump, Waters Xterra C18 column (5 μm 19 mm×50mm) and Micromass ZQ mass spectrometer, operating in positive ionelectrospray ionisation mode. Mobile phases A (0.1% formic acid inwater) and B (0.1% formic acid in acetonitrile) were used in a gradient;5% B to 100% over 7 min, held for 3 min, at a flow rate of 20 ml/min.

Analytical HPLC-MS

Analytical HPLC was carried out with a Spectra System P4000 pump andJones Genesis C18 column (4 μm, 50 mm×4.6 mm). Mobile phases A (0.1%formic acid in water) and B (acetonitrile) were used in a gradient of 5%B for 1 min rising to 98% B after 5 min, held for 3 min at a flow rateof 2 ml/min. Detection was by a TSP UV 6000LP detector at 254 nm UV andrange 210-600 nm PDA. The Mass spectrometer was a Finnigan LCQ operatingin positive ion electrospray mode.

NMR

¹H NMR spectra were recorded using Bruker DPX 300 spectrometer at 300MHz. Chemical shifts were reported in parts per million (ppm) on the δscale relative to tetramethylsilane internal standard. Unless statedotherwise all samples were dissolved in DMSO-d₆.

(a)4-[2-Fluoro-5-(4-oxo-3,4-dihydro-phthalazin-1-ylmethyl)-benzoyl]-piperazine-1-carboxylicacid tert-butyl ester (C)

To a stirred solution of the starting material D (850 g) indimethylacetamide (DMA) (3561 ml) at room temperature under nitrogen wasadded HBTU (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate) (1402 g) in one portion. Hünig's base (iPr₂NEt,1096 ml) was then added with the temperature kept between 15 to 25° C.followed by a solution of 1-Boc-piperazine (637 g) in DMA (1428 ml) withthe temperature kept between 15 to 25° C.

The solution was stirred at room temperature for 2 hours and sampled forcompletion (HPLC). Upon completion the solution was added to vigorouslystirred water (17085 ml) with the temperature kept between 15 to 25° C.and the solid filtered off, washing with water (2×7131 ml), hexane(2×7131 ml) and methyl tert-butyl ether (MTBE) (2×3561 ml). The solidwas then dried overnight and then sampled for water content and chemicalpurity.

This reaction was then repeated, see table:

Purity Water Content Batch Yield (g) (HPLC Area %) (K.F.) Correctedyield 1 1571.3 86.80 24.3 1032.5 g (78%) 2 2781.6 85.00 40.3 1411.5 g(106%) a. Greater than 100% yield attributed to non-representativesampling

(b) 4-[4-Fluoro-3-(piperazine-1-carbonyl)-benzyl]-2H-phthalazin-1-one(B)

To a stirred solution of industrial methylated spirits (IMS) (2200 ml)and concentrated HCl (4400 ml) was added compound C (2780.2 g) inportions at room temperature under nitrogen, the foaming was controlledby the addition rate. The solution was then stirred at 15 to 25° C. for30 minutes and sampled for completion (HPLC).

Upon completion the solution was evaporated to remove any IMS and theaqueous extracted with CH₂Cl₂ (2×3500 ml) before the pH was adjustedto >8 using concentrated ammonia. The resultant slurry was then dilutedwith water (10000 ml) and extracted with CH₂Cl₂ (4×3500 ml), washed withwater (2×2000 ml), dried over MgSO₄ (250 g) and evaporated. The crudeproduct was then slurried in CH₂Cl₂ (3500 ml) and added to MTBE (5000ml). The resultant suspension was filtered and dried at 50° C. overnightyielding 611.0 g (58.5% yield) of material with a purity of 94.12%

(c)4-[3-(4-Cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(A)

To a stirred suspension of compound B (1290 g) in CH₂Cl₂ (15480 ml)under nitrogen was added a pre-mixed solution of triethylamine (470 ml)and cyclopropane carbonyl chloride (306 ml) in CH₂Cl₂ (1290 ml) dropwisewith the temperature kept below 20° C. The solution was then stirred at10-15° C. for 15 minutes and sampled for completion. The reactionmixture was found to contain only 1.18% of starting material B and sothe reaction was deemed complete and the batch was then worked-up.

The reaction mixture was washed with water (7595 ml), 5% citric acidsolution (7595 ml), 5% sodium carbonate solution (7595 ml) and water(7595 ml). The organic layer was then dried over magnesium sulfate (500g).

The CH₂Cl₂ containing product layer was then isolated, filtered throughCelite and charged to a 251 vessel. CH₂Cl₂ (8445 ml) was then distilledout at atmospheric pressure and ethanol (10000 ml) added. Distillationwas then continued with every 4000 ml of distillate that was removedbeing replaced with ethanol (4000 ml) until the head temperature reached73.7° C. The reaction volume was then reduced (to 7730 ml) by which timethe head temperature had reached 78.9° C. and the solution was allowedto cool to 8° C. overnight. The solid was then filtered off, washed withethanol (1290 ml) and dried at 70° C. overnight.

Yield=1377.3 g (90%). HPLC purity (99.34% [area %]). Contained 4.93%ethanol and 0.45% CH₂Cl₂ by GC.

(d) Water Treatment of Compound A

A suspension of compound A (1377.0 g), as produced by the method ofExample 1, in water (13770 ml) was heated to reflux for 4 hours, cooledto room temperature and filtered. The solid was washed with water (2754ml) and dried at 70° C. overnight.

Yield=1274.8 g (92.6%). HPLC purity (99.49% [area %]). Contained 0.01%ethanol and 0.01% CH₂Cl₂ by GC.

¹H NMR spectrum of compound A (DMSO-d6) following the water treatment isshown in FIG. 1.

The powder XRD pattern of Compound A following the water treatment isshown in FIG. 2, which shows the compound is as Form A.

Example 2 Alternative Synthesis of Compound A Using1-(cyclopropylcarbonyl)piperazine

Methods (Also for Examples 3 & 4)NMR

¹H NMR spectra were recorded using Bruker DPX 400 spectrometer at 400MHz. Chemical shifts were reported in parts per million (ppm) on the δscale relative to tetramethylsilane internal standard. Unless statedotherwise all samples were dissolved in DMSO-d₆.

Mass Spectra

Mass spectra were recorded on an Agilent XCT ion trap mass spectrometerusing tandem mass spectrometry (MS/MS) for structural confirmation. Theinstrument was operated in a positive ion electrospray mode.

(a)4-[3-(4-Cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(Compound A)

2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzoic acid(D)(15.23 g, 51.07 mmol) was suspended with stirring under nitrogen inacetonitrile (96 ml). Diisopropylethylamine (19.6 ml, 112.3 mmol) wasadded followed by 1-cyclopropylcarbonylpiperazine (1)(9.45 g, 61.28mmol) and acetonitrile (1 ml). The reaction mixture was cooled to 18° C.O-Benzotriazol-1-yl-tetramethyluronium hexafluorophosphate (25.18 g,66.39 mmol) was added over 30 minutes and the reaction mixture wasstirred for 2 hours at room temperature. The reaction mixture was cooledto 3° C. and maintained at this temperature for 1 hour, before beingfiltered. The filter cake was washed with cold (3° C.) acetonitrile (20ml) before being dried in vacuo at up to 40° C. to give the titlecompound as a pale yellow solid (20.21 g).

Mass Spectrum: MH+ 435

1H NMR (400 MHz, DMSO-d6) δ: 0.70 (m, 4H), 1.88 (br s, 1H), 3.20 (br s,2H), 3.56 (m, 6H), 4.31 (s, 2H), 7.17 (t, 1H), 7.34 (dd, 1H), 7.41 (m,1H), 7.77 (dt, 1H), 7.83 (dt, 1H), 7.92 (d, 1H), 8.25 (dd, 1H), 12.53(s, 1H).

Example 3 Alternative Synthesis of Compound A Using1-(cyclopropylcarbonyl)piperazine HCl Salt

(a) 1-(Cyclopropylcarbonyl)piperazine HCl Salt (I′)

Acetic acid (700 ml) was treated with piperazine (50.00 g, 0.581 mol)portionwise over 15 minutes with stirring under nitrogen The reactionmixture was warmed to 40° C. and maintained at this temperature until acomplete solution was obtained. Cyclopropanecarbonyl chloride 59.2 ml,0.638 mol) was added over 15 minutes. The reaction mixture was stirredat room temperature overnight. The reaction mixture was filtered and thefiltrate distilled under reduced pressure until 430 ml of distillateshad been collected. Toluene (550 ml) was charged to the reaction mixtureand reduced pressure distillation continued until a further 400 ml ofdistillates were collected. A further charge of toluene (550 ml) wasadded and reduced pressure distillation continued until 350 ml ofdistillates were collected. The resulting slurry was diluted withtoluene (200 ml) and stirred overnight. Further toluene (500 ml) wasadded in order to mobilise the slurry. The slurry was filtered, washedwith toluene (100 ml) and dried in vacuo at 40° C. to give the titlecompound as an off white solid (86.78 g).

Mass Spectrum: MH+ 155

1H NMR (400 MHz, D₂O) δ: 0.92 (m, 4H), 1.98 (m, 1H), 3.29 (m, 2H), 3.38(m, 2H), 3.84 (m, 2H), 4.08 (m, 2H).

(b) Compound A

2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzoic acid(D)(0.95 g, 3.19 mmol) was suspended with stirring under nitrogen inacetonitrile (4 ml). 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate (HBTU) (1.45 g, 3.83 mmol) was added followed by1-cyclopropylcarbonylpiperazine HCl salt (I′)(0.73 g, 3.83 mmol).Diisopropylethylamine (1.39 ml, 7.98 mmol) was added over 3 minutes andthe reaction mixture was stirred for overnight at room temperature. Thereaction mixture was cooled to 5° C. and maintained at this temperaturefor 1 hour, before being filtered. The filter cake was washed with cold(3° C.) acetonitrile (2 ml) before being dried in vacuo at up to 40° C.to give the title compound as a pale yellow solid (0.93 g).

(c) Recrystallisation of Compound A from Aqueous Methanol

Compound A (9.40 g, 21.64 mmol) from step (b) was suspended in a mixtureof water (100 ml) and methanol (120 ml). The suspension was heated toreflux with stirring. The hazy solution produced was then cooled to 60°C. and filtered through a pad of harborlite. The filter pad was washedwith a mixture of water (5 ml) and methanol (5 ml). The filtrate wasdistilled at atmospheric pressure until 115 ml of distillate had beencollected. Distillation was then stopped and the suspension producedallowed to cool to room temperature. The resultant suspension wasstirred for ˜18 hours before being filtered. The filter cake was washedwith water (20 ml), before being dried in vacuo at up to 60° C. to givethe title compound in Form A as a white solid (8.67 g).

Mass Spectrum: MH+ 435

1H NMR (400 MHz, DMSO-d6) δ: 0.70 (m, 4H), 1.88 (br s, 1H), 3.20 (br s,2H), 3.56 (m, 6H), 4.31 (s, 2H), 7.17 (t, 1H), 7.34 (dd, 1H), 7.41 (m,1H), 7.77 (dt, 1H), 7.83 (dt, 1H), 7.92 (d, 1H), 8.25 (dd, 1H), 12.53(s, 1H).

(d) Recrystallisation of Compound A from Aqueous Ethanol

Compound A (9.40 g, 21.64 mmol) from step (b) was suspended in a mixtureof water (100 ml) and ethanol (50 ml). The suspension was heated toreflux with stirring. The hazy solution produced was then cooled to 60°C. and filtered through a pad of harborlite. The filter pad was washedwith a mixture of water (5 ml) and ethanol (5 ml). The filtrate wasdistilled at atmospheric pressure until 53 ml of distillate had beencollected. Distillation was then stopped and the suspension producedallowed to cool to room temperature. The resultant suspension wasstirred for ˜18 hours before being filtered. The filter cake was washedwith water (20 ml), before being dried in vacuo at 60° C. to give thetitle compound in Form A as a white solid (8.74 g).

Mass Spectrum: MH+435

1H NMR (400 MHz, DMSO-d6) δ: 0.70 (m, 4H), 1.88 (br s, 1H), 3.20 (br s,2H), 3.56 (m, 6H), 4.31 (s, 2H), 7.17 (t, 1H), 7.34 (dd, 1H), 7.41 (m,1H), 7.77 (dt, 1H), 7.83 (dt, 1H), 7.92 (d, 1H), 8.25 (dd, 1H), 12.53(s, 1H).

Example 4 Alternative Synthesis of Compound D

(a)2-Fluoro-5-[(E/Z)-(3-oxo-2-benzofuran-1(3H)-ylidene)methyl]benzonitrile(E)

Sodium t-amylate (99.00 g, 0.854 mol) and 2-methyltetrahydrofuran (960ml) were cooled to 2° C. under a nitrogen atmosphere. Diethyl phosphite(110 ml, 0.855 mol) was added dropwise maintaining the temperature at<5° C. 2-Methyltetrahydrofuran (40 ml) was added as line wash. Thereaction was stirred at 2° C. for 1 hour 40 minutes. A solution of2-carboxybenzaldehyde (H)(80 g, 0.533 mol) in 2-methyltetrahydrofuran(200 ml) was added, maintaining the temperature at <7° C. throughout theaddition. A line wash of 2-methyltetrahydrofuran (40 ml) was added. Thereaction mixture was warmed to 20° C. and held at 20° C. for 20 minutes.Methanesulphonic acid (66 ml, 1.01 mol) was added over 1 hour and 10minutes, followed by 2-methyltetrahydrofuran (40 ml). The reactionmixture was stirred at 20° C. over night. Methanesulphonic acid (7 ml,0.101 mol) was added, followed by 2-methyltetrahydrofuran (7 ml) and thereaction stirred at 20° C. for a further 4 hours. Water (400 ml) wasadded at room temperature and the resulting biphasic mixture stirred atroom temperature for 20 minutes. The lower aqueous layer was removed anda solution of potassium bicarbonate (53.50 g, 0.534 mol) in water (400ml) was added to the organic layer. The biphasic mixture was stirred atroom temperature for 20 minutes and then the lower aqueous solution wasremoved. The organic fraction was retained (solution of diethyl(3-oxo1,3-dihydro-2-benzofuran-1-yl)phosphonate).2-Fluoro-5-formylbenzonitrile (64 g, 0.429 mol) was added to the organicfraction and the mixture was stirred at 20° C. Triethylamine (66 ml,0.473 mol) was added dropwise followed by 2-methyltetrahydrofuran (7ml). The reaction mixture was stirred at 20° C. over night, then cooledto 5° C., filtered, washed with industrial methylated spirit (480 ml)and then dried in vacuo at up to 40° C. to give the title compound (91.2g).

Mass Spectrum: MH+ 266

1H NMR (400 MHz, DMSO-d6) δ: 6.89 (s, 1H, major isomer), 6.94 (s, 1H,minor isomer), 7.40 (dd, 1H, minor isomer), 7.58 (t, 1H, both isomers),7.70 (t, 1H, both isomers), 7.89 (t, 1H, both isomers), 7.95 (d, 1H,both isomers), 8.05 (d, 1H, both isomers), 8.15 (m, 2H, major isomer).

(b) 2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzonitrile(ED)

2-Fluoro-5-[(E/Z)-(3-oxo-2-benzofuran-1(3H)-ylidene)methyl]benzonitrile(E)(20 g, 75.40 mmol) and tetrahydrofuran (200 ml) were stirred at roomtemperature under a nitrogen atmosphere for 30 minutes. Hydrazinemonohydrate (4.40 ml, 90.53 mmol) was added, followed by a line wash oftetrahydrofuran (4 ml). The reaction mixture was stirred at roomtemperature for 1 hour 45 minutes. Acetic acid (1.10 ml, 19.20 mmol) wasadded and the reaction mixture warmed to 60° C. The reaction mixture washeld at 60° C. overnight. The reaction mixture was cooled to 50° C. andwater (200 ml) added dropwise. The temperature was maintained at 45° C.throughout the addition. The reaction mixture was cooled to 20° C.,filtered, washed with a mixture of water (30 ml) and tetrahydrofuran (30ml), and then dried in vacuo at up to 40° C. to give the title compound(18.7 g).

Mass spectrum: MH+280

1H NMR (400 MHz, DMSO-d6) δ: 4.38 (s, 2H), 7.46 (t, 1H), 7.72 (m, 1H),7.85 (dt, 1H), 7.92 (m, 2H), 7.99 (d, 1H), 8.27 (dd, 1H), 12.57 (s, 1H).

(c) 2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzoic acid(D)

2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzonitrile (ED)(9.60 g, 34.37 mmol) and water (40 ml) were stirred at 20° C. 2M Sodiumhydroxide (36 ml, 72.00 mmol) was added, the reaction mixture warmed to90° C. and held at this temperature overnight. The reaction mixture wascooled to room temperature and filtered. The filter pad was washed withwater (10 ml) and the combined filtrate added to 2M HCl (56 ml, 112.00mmol) at 60° C. over 40 minutes. The resulting suspension was cooled to50° C. and filtered, washed with water (57 ml) and dried in vacuo at upto 60° C. to give the title compound as a white solid (9.72 g).

Mass Spectrum: MH+ 299

1H NMR (400 MHz, DMSO-d6) δ: 4.36 (s, 2H), 7.24 (dd, 1H), 7.59 (m, 1H),7.84 (dt, 2H), 7.90 (dt, 1H), 7.98 (d, 1H), 8.27 (dd, 1H), 12.59 (s,1H), 13.22 (br s, 1H).

Example 5 Recrystallisation of Compound A from Aqueous Ethanol

4-(3-{[4-(cyclopropylcarbonyl)piperazin-1-yl]carbonyl}-4-fluorobenzyl)phthalazin-1(2H)-one(compound A) (20.00 g, 44.66 mmol) was suspended in a mixture of water(50 ml) and ethanol (150 ml). The suspension was heated to reflux withstirring. The solution produced was then cooled to 70° C. and filtered.The filter pad was washed with a mixture of water (8 ml) and ethanol (22ml).

The filtrate was cooled to 45° C. with stirring.4-(3-{[4-(cyclopropylcarbonyl)piperazin-1-yl]carbonyl}-4-fluorobenzyl)phthalazin-1(2H)-one(Compound A) in Form A (0.08 g) was added in order to seed the mixture.The resulting suspension was cooled to 20° C. over 2.5 hours and wasstirred at this temperature for a further 16 hours in order to establishcrystallisation. Water (200 ml) was added over 5 hours maintaining thetemperature at 20° C. At the end of the addition the suspension was heldat 20° C. for 2 hours.

The suspension was filtered and the filter cake washed with a mixture ofethanol (24 ml) and water (56 ml). The isolated solid was discharged anddried under vacuum at 40-60° C., to give the title compound (Form A) asan off white solid (18.1 g).

Methods for obtaining FIG. 3 of 5

Powder XRD—FIG. 3 (Compound A as Form A)

Powder X-ray diffraction was recorded with a Bruker D5000 diffractometer(wavelength of X-rays 1.5418 Å Cu source, Voltage 40 kV, filamentemission 40 mA). Samples were scanned from 2-40° 2θ using a 0.02° stepwidth and a 4 second time count.

Powder XRD—FIG. 4 (Compound A as Solvated Form)

Powder X-ray diffraction of the solvate family was recorded with a InelXRG-3000 diffractometer (wavelength of X-rays 1.5418 Å Cu source,Voltage 40 kV, filament emission 30 mA), fitted with a curved positionsensitive detector (range 120° 2θ). Samples were scanned from 2.5-40° 2θusing a 0.030 step width typically with a total collection time of 300s.

Differential Scanning Calorimetry (DSC)—FIG. 5

DSC was recorded using a Mettler DSC820E with TSO801RO robotic system.Typically less than 5 mg of material, contained in a 40 μl aluminium panfitted with a pierced lid, was heated over the temperature range 25° C.to 325° C. at a constant heating rate of 10° C. per minute. A nitrogenpurge gas was used with flow rate 100 ml per minute.

Example 6 Inhibitory Action

In order to assess the inhibitory action of the active compound, thefollowing assay was used to determine an IC₅₀ value.

Mammalian PARP, isolated from Hela cell nuclear extract, was incubatedwith Z-buffer (25 mM Hepes (Sigma); 12.5 mM MgCl₂ (Sigma); 50 mM KCl(Sigma); 1 mM DTT (Sigma); 10% Glycerol (Sigma) 0.001% NP-40 (Sigma); pH7.4) in 96 well FlashPlates (TRADE MARK) (NEN, UK) and varyingconcentrations of said inhibitors added. All compounds were diluted inDMSO and gave final assay concentrations of between 10 and 0.01 μM, withthe DMSO being at a final concentration of 1% per well. The total assayvolume per well was 40 μl.

After 10 minutes incubation at 30° C. the reactions were initiated bythe addition of a 10 μl reaction mixture, containing NAD (5 μM), ³H-NADand 30mer double stranded DNA-oligos. Designated positive and negativereaction wells were done in combination with compound wells (unknowns)in order to calculate % enzyme activities. The plates were then shakenfor 2 minutes and incubated at 30° C. for 45 minutes.

Following the incubation, the reactions were quenched by the addition of50 μl 30% acetic acid to each well. The plates were then shaken for 1hour at room temperature.

The plates were transferred to a TopCount NXT™ (Packard, UK) forscintillation counting. Values recorded are counts per minute (cpm)following a 30 second counting of each well.

The % enzyme activity for the compound is then calculated using thefollowing equation:

${\%\mspace{11mu}{Inhibition}} = {100 - \left( {100 \times \frac{\begin{pmatrix}{{{cpm}\mspace{14mu}{of}\mspace{14mu}{unknowns}} -} \\{{mean}\mspace{14mu}{negative}\mspace{14mu}{cpm}}\end{pmatrix}}{\begin{pmatrix}{{{mean}\mspace{14mu}{positive}\mspace{14mu}{cpm}} -} \\{{mean}\mspace{14mu}{neagative}\mspace{14mu}{cpm}}\end{pmatrix}}} \right)}$

IC₅₀ values (the concentration at which 50% of the enzyme activity isinhibited) were calculated, which are determined over a range ofdifferent concentrations, normally from 10 μM down to 0.001 μM. SuchIC₅₀ values are used as comparative values to identify increasedcompound potencies.

Compound A has an IC₅₀ of about 5 nM.

Potentiation Factor

The Potentiation Factor (PF₅₀) for the active compound is calculated asa ratio of the IC₅₀ of control cell growth divided by the IC₅₀ of cellgrowth+PARP inhibitor. Growth inhibition curves for both control andcompound treated cells are in the presence of the alkylating agentmethyl methanesulfonate (MMS). The test compound was used at a fixedconcentration of 0.2 micromolar. The concentrations of MMS were over arange from 0 to 10 μg/ml.

Cell growth was assessed using the sulforhodamine B (SRB) assay (Skehan,P., et al., (1990) New colorimetric cytotoxicity assay foranticancer-drug screening. J. Natl. Cancer Inst. 82, 1107-1112.). 2,000HeLa cells were seeded into each well of a flat-bottomed 96-wellmicrotiter plate in a volume of 100 μl and incubated for 6 hours at 37°C. Cells were either replaced with media alone or with media containingPARP inhibitor at a final concentration of 0.5, 1 or 5 μM. Cells wereallowed to grow for a further 1 hour before the addition of MMS at arange of concentrations (typically 0, 1, 2, 3, 5, 7 and 10 μg/ml) toeither untreated cells or PARP inhibitor treated cells. Cells treatedwith PARP inhibitor alone were used to assess the growth inhibition bythe PARP inhibitor.

Cells were left for a further 16 hours before replacing the media andallowing the cells to grow for a further 72 hours at 37° C. The mediawas then removed and the cells fixed with 100 μl of ice cold 10% (w/v)trichloroacetic acid. The plates were incubated at 4° C. for 20 minutesand then washed four times with water. Each well of cells was thenstained with 100 μl of 0.4% (w/v) SRB in 1% acetic acid for 20 minutesbefore washing four times with 1% acetic acid. Plates were then driedfor 2 hours at room temperature. The dye from the stained cells wassolubilized by the addition of 100 μl of 10 mM Tris Base into each well.Plates were gently shaken and left at room temperature for 30 minutesbefore measuring the optical density at 564 nM on a Microquantmicrotiter plate reader.

Compound A has a PF₅₀ at 200 nM of at least 20.

1. A method of obtaining4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) as crystalline Form A comprising the steps of: (i)crystallising4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-onefrom a solvent; (ii) if the original solvent is not ethanol, treatingthe crystalline compound A with ethanol; (iii) treating the crystallinecompound A containing trapped ethanol obtained from either step (i) orstep (ii) with water to remove trapped ethanol; (iv) drying theresulting product.
 2. A method of obtaining4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) as crystalline Form A comprising the steps of: (i)crystallising4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-onefrom a solvent; (ii) if the original solvent used in the synthesis ofcompound A in the crystalline form is not a mixture of water and a C₁₋₂alcohol, heating the compound with a mixture of water and a C₁₋₂alcohol; (iii) distilling the mixture from step (ii) at ambientpressure; and (iv) drying the resulting product from step (iii).
 3. Amethod of obtaining4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-one(compound A) as crystalline Form A comprising the steps of: (i)suspending compound A in a mixture of water and a C₁₋₂ alcohol as thesolvent; (ii) heating the suspension from step (i) to reflux; (iii)cooling the solution from step (ii) and seeding with compound A as FormA; (iv) drying the resulting product from step (iii).
 4. A method ofsynthesising4-[3-(4-cyclopropanecarbonyl-piperazine-1-carbonyl)-4-fluoro-benzyl]-2H-phthalazin-1-onefrom 4-[4-fluoro-3-(piperazine-1-carbonyl)-benzyl]-2H-phthalazin-1-Onecomprising the step of: (i) adding a pre-mixed solution of triethylamineand cyclopropane carbonyl chloride, in an organic solvent, to4-[4-fluoro-3-(piperazine-1-carbonyl)-benzyl]-2H-phthalazin-1-one in thesame organic solvent with the temperature of the solution beingcontrolled to be below
 2000. 5. A method synthesising2-fluoro-5-(4-oxo-3,4-dihydro-phthalazin-1-ylmethyl)-benzoic acid,comprising the step of: (i) synthesising diethyl(3-oxo-1,3-dihydro-2-benzofuran-1-yl)phosphonate from2-carboxybenzaldehyde by reaction with the sodium salt of diethylphosphite, followed by reaction with methanesulphonic acid; (ii)synthesising2-fluoro-5-[(E/Z)-(3-oxo-2-benzofuran-1(3H)-ylidene)methyl]benzonitrilefrom diethyl (3-oxo-1,3-dihydro-2-benzofuran-1-yl)phosphonate, byreaction with triethylamine in 2-methyltetrahydrofuran.
 6. The method ofclaim 5, further comprising the step of: (i) synthesising2-fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzonitrile (ED):

from compound E:

by reaction with hydrazine hydrate; and (ii) synthesising compound D:

from compound ED by reaction with sodium hydroxide. 7.2-Fluoro-5-[(4-oxo-3,4-dihydrophthalazin-1-yl)methyl]benzonitrile (ED):